If they were injured initially with high ammonia and/or nitrite when they were first introduced to the tank (if it was still cycling), that will shorten their natural lifespan. Not saying it happened with your tank, but it could have happened anytime since they were born.
To put it like cars (I had to buy new tires this week!), its like you get 60,000 miles if all goes well. But high ammonia and nitrite puts a lot of wear/tear on their bodies and even though they appear healthy, they may be at 50,000 miles!
I applaud you in this decision. Its really not fair to keep a molly in so small a tank. Wait until you get the 30 gallon!
To put it like cars (I had to buy new tires this week!), its like you get 60,000 miles if all goes well. But high ammonia and nitrite puts a lot of wear/tear on their bodies and even though they appear healthy, they may be at 50,000 miles!
I applaud you in this decision. Its really not fair to keep a molly in so small a tank. Wait until you get the 30 gallon!